Conventionally, there is well known a device or a method for detecting an abnormality of an assembled battery constructed with a plurality of rechargeable single batteries connected in series. For example, Japanese Unexamined Patent Publication No. 11-252809 discloses a battery pack overcharge/overdischarge preventing control device in which a protective circuit makes a self-diagnosis to determine whether a protective circuit of a secondary battery normally operates. The battery pack overcharge/overdischarge preventing control device determines whether the protective circuit normally operates by comparing a total cell voltage, in which cell voltages at a plurality of secondary batteries detected by a cell voltage detection circuit are added to each other, to a battery voltage detected by a battery voltage detection circuit. In control of the battery pack overcharge/overdischarge preventing control device, when a switching circuit is turned off to interrupt a charge or discharge current, whether the protective circuit normally operates is determined based on whether a current value output from a current detection circuit is 0 and whether the battery voltage output from the battery voltage detection circuit is greater than or equal to a voltage necessary for a control circuit to operate.
Japanese Unexamined Patent Publication No. 2005-168118 discloses an assembled-battery abnormality detection device that detects a disconnection between a cell and a detection terminal even if the cell is in the overcharge or overdischarge state. In the assembled-battery abnormality detection device, a circuit that detects the overcharge and overdischarge of the cell outputs a disconnection diagnosis making signal, whereby MOS transistors each provided to a corresponding cell are alternately turned on and off forcedly and the turned-on/off MOS transistors are switched and alternately turned on and off. The assembled-battery abnormality detection device detects the disconnection of a connection line between the cell and the corresponding detection terminal based on a signal detected from an abnormality detection circuit at that time.
Japanese Unexamined Patent Publication No. 2010-025925 discloses an assembled-battery voltage detection device that prevents the false determination that the disconnection is generated although the disconnection is not generated in wiring to an assembled battery. In the assembled-battery voltage detection device, a voltage detection line is extracted from each of a plurality of voltage input terminals, a capacitor is interposed in each coupling line coupling two voltage detection lines adjacent to each other, and each voltage detection line is connected to a voltage detection unit. In the assembled-battery voltage detection device, the voltage detection line located on a positive electrode side of each cell is connected to a ground through one or a plurality of disconnection detecting resistors, and the disconnection of the wiring between a plurality of voltage detection points and a plurality of voltage input terminals of the assembled battery is detected based on an input voltage from each voltage detection line. In the assembled-battery voltage detection device, in the case that the disconnection is generated in a wire harness at the end of the assembled battery, because the voltages at both the ends of the corresponding capacitor substantially are 0, the determination that the disconnection is generated in the wire harness at the end can be made when the voltage at both the ends lowers to a predetermined threshold.
Japanese Unexamined Patent Publication No. 2012-050316 discloses a power supply device that detects disconnections of all the voltage detection lines and surely detects the voltage at the battery cell. The power supply device includes a battery block that is constructed with a plurality of battery cells connected in series, a voltage detection circuit that detects the voltage at each battery cell through the voltage detection line, and a disconnection detection circuit that detects the disconnection of the voltage detection line from a detected voltage of the voltage detection circuit. The disconnection detection circuit determines the disconnection of the voltage detection line if the detected voltage at the battery cell is smaller than a predetermined voltage value or if a voltage difference between the detected voltage value at the battery cell and a predetermined voltage value is larger than a set value.